Abstract
After nearly a century of fire exclusion in many central and southern Sierra Nevada mixed-conifer forests, dead and down surface fuels have reached high levels without the recurring fires that consume the accumulated organic matter. The effects of prescribed fires used to reduce fuel loads and restore fire have been monitored in Yosemite, Sequoia, and Kings Canyon National Parks for over 30 years. Ten years following prescribed fire treatments in Sequoia and Kings Canyon, mean total fuel loads accumulated to 84 percent of pre-fire levels in ponderosa pine forests, 83 percent in white fir-mixed conifer, and 66 percent in giant sequoia-mixed conifer forests. Thirty-one years after burning, mean fuel load of fine and sound woody fuels increased in ponderosa pine research plots in Yosemite. Most fuel accumulation appeared to occur within the first decade after fire, however the post-fire fuel complex was different than that pre-fire. In areas that have remained unburned, surface fuel accumulation appears to be relatively slow and may indicate that decay rates have approached accumulation rates for the mixed-conifer forest types. This long-term information has important implications for fire management planning, including scheduling fuel hazard reduction and subsequent maintenance treatments.
Highlights
As a result of a long period of fire exclusion, heavy accumulations of fuels in many western forests are of concern to managers and the public (Leopold et al 1963, Towell 1969, Kilgore 1972)
The study sites are located in Yosemite National Park, in the central Sierra Nevada, and Sequoia and Kings Canyon National Parks in the southern Sierra Nevada, California (Figure 1)
Following initial treatment with prescribed fire, total fuel load was reduced by 99 percent
Summary
As a result of a long period of fire exclusion, heavy accumulations of fuels in many western forests are of concern to managers and the public (Leopold et al 1963, Towell 1969, Kilgore 1972) These altered fuel conditions can promote uncharacteristically intense and/or extensive fires that may have undesirable effects (Hartesveldt 1964, Kilgore 1972, van Wagtendonk 1985). Throughout the forests of the central and southern Sierra Nevada, fire exclusion for many decades has resulted in heavy surface fuel accumulation and altered forest structure (Biswell et al 1968, Kilgore 1972, Parsons 1978, Vankat and Major 1978) While these changes have long been recognized, efforts to restore fuel and forest conditions in the past have been intermittent and small scale compared to the extent of the affected area. Land management agencies including the National Park Service have increased efforts to use prescribed fire to reduce the fuel hazards and restore fuel and vegetation conditions
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